Method for compensating mismatch of in-phase signal and quadrature signal of transmitter/receiver

ABSTRACT

A method for compensating mismatches of an in-phase signal and a quadrature signal of a transmitter/receiver is provided. The method includes: receiving a plurality of test signals to generate two groups of factors, respectively, where each group of factors is applied to two multipliers utilized for compensating a gain mismatch and a phase mismatch of the in-phase signal and the quadrature signal of the transmitter/receiver; then calculating a delay mismatch of the in-phase signal and the quadrature signal according to the two groups of factors.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for compensating a mismatch ofan in-phase signal and a quadrature signal of a receiver or atransmitter, and more particularly, to a method for compensating gainmismatch/phase mismatch/path delay mismatch of an in-phase signal and aquadrature signal of a receiver or a transmitter.

2. Description of the Prior Art

In a conventional zero-IF (zero intermediate frequency) receiver, aradio frequency signal can be directly converted into a baseband signal.Because there is no middle frequency required to be selected, the imagefrequency interference of a super-heterodyne receiver will not behappened in the zero-IF receiver, and the zero-IF receiver does not needa high quality filter. In addition, because the zero-IF receiverincludes only one local oscillator (i.e. only one phase noise source),the zero-IF receiver does not need large and expensive filter, and canbe simply integrated. However, in the zero-IF receiver, the in-phasesignal and the quadrature signal may have I/Q mismatch issue because theoscillation signals supplied to the in-phase channel and the quadraturechannel are not matched. In addition, because the path delays of thein-phase channel and the quadrature channel may be different, thein-phase signal and the quadrature signal may also have the path delaymismatch issue.

Because the gain mismatch/phase mismatch/path delay mismatch of thein-phase signal and the quadrature signal may influence the followingsignal processing operation (e.g., the bit error rate (BER) increases),how to design a method for estimating and compensating the gainmismatch/phase mismatch/path delay mismatch of the in-phase signal andthe quadrature signal is an important topic.

SUMMARY OF THE INVENTION

It is therefore an objective of the present invention to provide amethod for compensating gain mismatch/phase mismatch/path delay mismatchof an in-phase signal and a quadrature signal of a receiver or atransmitter, to solve the above-mentioned problem.

According to one embodiment of the present invention, a method forcompensating a mismatch of an in-phase signal and a quadrature signal ofa receiver is disclosed, where the receiver comprises a first channel, asecond channel and a second multiplier, where the first channelcomprises: a first mixer, for mixing a received signal with a firstlocal oscillation signal to generate a first signal; a first multiplier,coupled to the first mixer, for generating an adjusted first signalaccording to the first signal; and an adder, coupled to the firstmultiplier; the second channel comprises: a second mixer, for mixing thereceived signal with a second local oscillation signal to generate asecond signal; and an adjustable delay unit, coupled to the secondmixer, for delaying the second signal to generate a delayed secondsignal; and the second multiplier is coupled between the adjustabledelay unit and the adder, and is used for generating an adjusted secondsignal according to the delayed second signal, where the adder adds theadjusted first signal and the adjusted second signal to generate acompensated first signal; the compensated first signal is one of thein-phase signal and the quadrature signal, and the delayed second signalis the other one of the in-phase signal and the quadrature signal; andthe method comprises: disabling the adjustable delay unit; receiving afirst test signal to serve as the received signal to determine a firstgroup of factors of the first multiplier and the second multiplier;receiving a second test signal to serve as the received signal todetermine a second group of factors of the first multiplier and thesecond multiplier; and calculating a delay amount of the adjustabledelay unit according to the first group of factors and the second groupof factors.

According to another embodiment of the present invention, a method forcompensating a mismatch of an in-phase signal and a quadrature signal ofa receiver is disclosed, where the receiver comprises a first channel, asecond channel and a second multiplier, where the first channelcomprises: a first mixer, for mixing a received signal with a firstlocal oscillation signal to generate a first signal; an adjustable delayunit, coupled to the first mixer, for delaying the first signal togenerate a delayed first signal; a first multiplier, coupled to theadjustable delay unit, for generating an adjusted first signal accordingto the delayed first signal; and an adder, coupled to the firstmultiplier; the second channel comprises: a second mixer, for mixing thereceived signal with a second local oscillation signal to generate asecond signal; and the second multiplier is coupled between the secondmixer and the adder, and is used for generating an adjusted secondsignal according to the second signal, wherein the adder adds theadjusted first signal and the adjusted second signal to generate acompensated first signal; where the compensated first signal is one ofthe in-phase signal and the quadrature signal, and the second signal isthe other one of the in-phase signal and the quadrature signal; and themethod comprises: disabling the adjustable delay unit; receiving a firsttest signal to serve as the received signal to determine a first groupof factors of the first multiplier and the second multiplier; receivinga second test signal to serve as the received signal to determine asecond group of factors of the first multiplier and the secondmultiplier; and calculating a delay amount of the adjustable delay unitaccording to the first group of factors and the second group of factors.

According to another embodiment of the present invention, a method forcompensating a mismatch of an in-phase signal and a quadrature signal ofa transmitter is disclosed, wherein the transmitter comprises a firstchannel, a second multiplier and a second channel, where the firstchannel, comprises: a first multiplier, for receiving a first signal togenerate a first adjusted first signal; and a first mixer, coupled tothe first multiplier, for mixing the adjusted first signal with a firstlocal oscillation signal to generate a mixed first signal; the secondmultiplier is for receiving the first signal to generate a secondadjusted first signal; the second channel comprises: an adder, coupledto the second multiplier, for adding the second adjusted first signaland a second signal to generate an adjusted second signal; an adjustabledelay unit, coupled to the adder, for delaying the adjusted secondsignal to generate a delayed second signal; and a second mixer, coupledto the adjustable delay unit, for mixing the delayed second signal witha second local oscillation signal to generate a mixed second signal;where the first adjusted first signal is one of the in-phase signal andthe quadrature signal, and the delayed second signal is the other one ofthe in-phase signal and the quadrature signal; and the method comprises:disabling the adjustable delay unit; transmitting a first test signaland a second test signal to serve as the first signal and the secondsignal, respectively, to determine a first group of factors of the firstmultiplier and the second multiplier; transmitting a third test signaland a fourth test signal to serve as the first signal and the secondsignal, respectively, to determine a second group of factors of thefirst multiplier and the second multiplier; and calculating a delayamount of the adjustable delay unit according to the first group offactors and the second group of factors.

According to another embodiment of the present invention, a method forcompensating a mismatch of an in-phase signal and a quadrature signal ofa transmitter is disclosed, where the transmitter comprises firstchannel, a second multiplier and a second channel, where the firstchannel comprises: a first multiplier, for receiving a first signal togenerate a first adjusted first signal; an adjustable delay unit,coupled to the first multiplier, for delaying the first adjusted firstsignal to generate a delayed first signal; and a first mixer, coupled tothe adjustable delay unit, for mixing the delayed first signal with afirst local oscillation signal to generate a mixed first signal; thesecond multiplier is for receiving the first signal to generate a secondadjusted first signal; the second channel comprises: an adder, coupledto the second multiplier, for adding the second adjusted first signaland a second signal to generate an adjusted second signal; and a secondmixer, coupled to the adjustable delay unit, for mixing the adjustedsecond signal with a second local oscillation signal to generate a mixedsecond signal; where the delayed first signal is one of the in-phasesignal and the quadrature signal, and the adjusted second signal is theother one of the in-phase signal and the quadrature signal; and themethod comprises: disabling the adjustable delay unit; transmitting afirst test signal and a second test signal to serve as the first signaland the second signal, respectively, to determine a first group offactors of the first multiplier and the second multiplier; transmittinga third test signal and a fourth test signal to serve as the firstsignal and the second signal, respectively, to determine a second groupof factors of the first multiplier and the second multiplier; andcalculating a delay amount of the adjustable delay unit according to thefirst group of factors and the second group of factors.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a gain mismatch/phase mismatch/pathdelay mismatch of an in-phase signal and a quadrature signal of a priorart receiver.

FIG. 2 is a diagram illustrating a diagram illustrating a receiveraccording to one embodiment of the present invention.

FIG. 3 is a flowchart of a method for compensating a mismatch of thein-phase signal and the quadrature signal of the receiver according toone embodiment of the present invention.

FIG. 4 is a diagram illustrating a diagram illustrating a receiveraccording to another embodiment of the present invention.

FIG. 5 is a diagram illustrating a gain mismatch/phase mismatch/pathdelay mismatch of an in-phase signal and a quadrature signal of a priorart transmitter.

FIG. 6 is a diagram illustrating a diagram illustrating a transmitteraccording to one embodiment of the present invention.

FIG. 7 is a flowchart of a method for compensating a mismatch of thein-phase signal and the quadrature signal of the transmitter accordingto one embodiment of the present invention

FIG. 8 is a diagram illustrating a diagram illustrating a transmitteraccording to another embodiment of the present invention.

DETAILED DESCRIPTION

Certain terms are used throughout the following description and claimsto refer to particular system components. As one skilled in the art willappreciate, manufacturers may refer to a component by different names.This document does not intend to distinguish between components thatdiffer in name but not function. In the following discussion and in theclaims, the terms “including” and “comprising” are used in an open-endedfashion, and thus should be interpreted to mean “including, but notlimited to . . . ” The terms “couple” and “couples” are intended to meaneither an indirect or a direct electrical connection. Thus, if a firstdevice couples to a second device, that connection may be through adirect electrical connection, or through an indirect electricalconnection via other devices and connections.

Please refer to FIG. 1, which is a diagram illustrating a gainmismatch/phase mismatch/path delay mismatch of an in-phase signal and aquadrature signal of a prior art receiver 100, where the receiver 100includes two mixers 110 and 120; and a path delay 130 shown in FIG. 1 isused to represent a delay difference between an in-phase channel and aquadrature channel, and is not a circuit element. As shown in FIG. 1,the receiver 100 receives a signal that is represented ascos((w_(LO)+w_(m))*t), and the signal passes through the mixers 110 and120 and the path delay 130 to generate the in-phase signal I and thequadrature signal Q, respectively, where the in-phase signal I can berepresented as (1+G)cos(w_(m)t−P), and the quadrature signal Q can berepresented as sin(w_(m)(t−dt)), where “G” is a value of I/Q gainmismatch, “P” is a value of I/Q phase mismatch, the “dt” is a value ofI/Q path delay mismatch, and the “G” value and the “P” value aregenerated due to the mismatch of two local oscillation signals generatedfrom a local oscillator and supplied to the mixers 110 and 120.

Therefore, the objective of the present invention is to provide areceiver whose in-phase signal I and quadrature signal Q are close totheir ideal values, that is cos(w_(m)t) and sin(w_(m)t), respectively.

Please refer to FIG. 2, which is a diagram illustrating a diagramillustrating a receiver 200 according to one embodiment of the presentinvention. As shown in FIG. 2, the receiver 200 includes a first channel210, a second channel 220 and a multiplier 230, where the first channel210 includes a mixer 212, a multiplier 214 and an adder 216, and thesecond channel 220 includes a mixer 222 and an adjustable delay unit224. In addition, the receiver 200 further includes a control unit (notshown) that is used to generate control signals according to outputs ofthe first channel 210 and the second channel 220, and the control unituses the control signals to adjust a factor X of the multiplier 214, afactor Y of the multiplier 230 and a delay amount of the adjustabledelay unit 224. In addition, in this embodiment, the receiver 200 is azero-IF receiver, but it is not meant to be a limitation of the presentinvention.

In the operations of the receiver 200, the mixer 212 mixes a receivedsignal Vin with a local oscillation signal OS1 to generate an in-phasesignal I, the multiplier 214 multiplies the in-phase signal I by thefactor X to generate an adjusted in-phase signal Iadj. In addition, themixer 222 mixes the received signal Vin with a local oscillation signal052 to generate a quadrature signal Q, and the adjustable delay unit 224delays the quadrature signal Q to generate a delayed quadrature signalQmatch. Then, the multiplier 230 multiplies the delayed quadraturesignal Qmatch by the factor Y to generate an adjusted quadrature signalQadj. Finally, the adder 216 adds the adjusted in-phase signal Iadj andthe adjusted quadrature signal Qadj to generate a compensated in-phasesignal Imatch.

Please refer to FIG. 2 and FIG. 3 together, FIG. 3 is a flowchart of amethod for compensating a mismatch of the in-phase signal I and thequadrature signal Q of the receiver 200 according to one embodiment ofthe present invention. Referring to FIG. 3, the flow is described asfollows.

In Step 300, the adjustable delay unit 224 is disabled, that is thedelay amount of the adjustable delay unit 224 is set to be 0. In Step302, the receiver 200 receives a first test signal, where the first testsignal is a single tone signal having a frequency f1. Then, the controlunit (not shown) adjusts the factor X of the multiplier 214 and thefactor Y of the multiplier 230 by referring to an image rejection ratio(IRR) calculated by using the compensated in-phase signal Imatch and thedelayed quadrature signal Qmatch to obtain a first group of factors (X1,Y1), where when using the first group of factors (X1, Y1) the receiver200 has the optimal IRR. Referring to FIG. 1 and FIG. 2, assuming thatthe outputs of the mixers 212 and 222 are (1+G)cos(w_(m)t−P) andsin(w_(m)(t−dt)), respectively, shown in FIG. 1, the value of Y1 shouldbe close to (−tan(P+2πf1*dt)) when the compensated in-phase signalImatch and the delayed quadrature signal Qmatch have the optimal IRR.

In Step 304, the receiver 200 receives a second test signal, where thesecond test signal is a single tone signal having a frequency f2. Then,the control unit (not shown) adjusts the factor X of the multiplier 214and the factor Y of the multiplier 230 by referring to the IRRcalculated by using the compensated in-phase signal Imatch and thedelayed quadrature signal Qmatch to obtain a second group of factors(X2, Y2), where when using the second group of factors (X2, Y2) thereceiver 200 has the optimal IRR. Referring to FIG. 1 and FIG. 2,assuming that the outputs of the mixers 212 and 222 are(1+G)cos(w_(m)t−P) and sin(w_(m)(t−dt)), respectively, shown in FIG. 1,the value of Y2 should be close to (−tan(P+2πf2*dt)) when thecompensated in-phase signal Imatch and the delayed quadrature signalQmatch have the optimal IRR.

In Step 306, the control unit uses the first group of factors (X1, Y1)and the second group of factors (X2, Y2) to calculate a delay amount ofthe adjustable delay unit 224. In detail, because in Steps 302 and 304it is calculated that: Y1≈(−tan(P+2πf1*dt)) and Y2≈(−tan(P+2πf2*dt)),the delay amount dt between the in-phase signal I and the quadraturesignal Q can be calculated by using the following formula:dt≈(Y1−Y2)/(2π(f2−f1)).

In addition, because dt=Δ*Ts=Δ/Fs, where Ts and Fs are a sampling clockperiod and a sampling clock frequency of an analog-to-digital converter(ADC) of the receiver 200, respectively, a delay parameter Δ used by theadjustable delay unit 224 can be calculated as follows:

${\Delta = {\frac{( {{Y\; 1} - {Y\; 2}} )}{\frac{2{\pi( {{f\; 2} - {f\; 1}} )}}{Fs}} = \frac{( {{Y\; 1} - {Y\; 2}} )}{\frac{2{\pi( {{{tone\_ idx}( {f\; 2} )} - {{tone\_ idx}( {f\; 1} )}} )}}{FFT\_ pts}}}},$where FFT_pts is a number of points used when performing a fast FourierTransform upon the first test signal and the second test signal, andtone_index is an index of the tone/frequency.

In Step 308, the control unit (not shown) enables the adjustable delayunit 224 and sets adjustable delay unit 224 according to the delayparameter Δ or the delay amount dt.

In Step 310, the receiver 200 receives a third test signal, where thethird test signal is a single tone signal having a frequency f3. Then,the control unit (not shown) adjusts the factor X of the multiplier 214and the factor Y of the multiplier 230 by referring to the IRRcalculated by using the compensated in-phase signal Imatch and thedelayed quadrature signal Qmatch to obtain a third group of factors (X3,Y3), where when using the third group of factors (X3, Y3) the receiver200 has the optimal IRR. The third group of factors (X3, Y3) are used bythe multipliers 214 and 230 of the receiver 200 in the followingoperations.

In light of above, after the delay parameter Δ used in adjustable delayunit 224, the factor X3 of the multiplier 214 and the factor Y3 of themultiplier 230 are determined, the receiver 200 can eliminate the gainmismatch/phase mismatch/path delay mismatch of the in-phase signal I andthe quadrature signal Q, and the gain/phase/path delay of thecompensated in-phase signal Imatch and the delayed quadrature signalQmatch are matched. In particular, when eliminating the path delaymismatch of the in-phase signal I and the quadrature signal Q, thereceiver 200 can simultaneously eliminate the frequency-dependent phasemismatch and the frequency-independent phase mismatch.

It is noted that, in the embodiment shown in FIG. 2, the first channel210 is the in-phase channel and the second channel 220 is the quadraturechannel. In other embodiments, however, the first channel 210 can be thequadrature channel and the second channel 220 can be the in-phasechannel, and the determination steps of the delay parameter Δ, thefactor X3 of the multiplier 214 and the factor Y3 of the multiplier 230are similar to the steps shown in FIG. 3 (only the formula forcalculating the delay parameter Δ is different from the formuladescribed in step 306). Because a person skilled in this art shouldunderstand how to derive the formula to obtain the delay parameter Δ andthe two factors X3 and Y3 after reading the above-mentioned disclosure,further descriptions are omitted here.

Please refer to FIG. 4, which is a diagram illustrating a receiver 400according to another embodiment of the present invention. As shown inFIG. 4, the receiver 400 includes a first channel 410, a second channel420 and a multiplier 430, where the first channel 410 includes a mixer412, an adjustable delay unit 414, a multiplier 416 and an adder 418,and the second channel 420 includes a mixer 422. In addition, thereceiver 400 further includes a control unit (not shown) that is used togenerate control signals according to outputs of the first channel 410and the second channel 420, and the control unit uses the controlsignals to adjust a factor X of the multiplier 416, a factor Y of themultiplier 430 and a delay amount of the adjustable delay unit 414.

In the operations of the receiver 400, the mixer 412 mixes a receivedsignal Vin with a local oscillation signal OS1 to generate an in-phasesignal I, the adjustable delay unit 414 delays the in-phase signal I togenerate a delayed in-phase signal Id, and the multiplier 416 multipliesthe delayed in-phase signal Id by the factor X to obtain an adjustedin-phase signal Iadj. In addition, the mixer 422 mixes the receivedsignal Vin with a local oscillation signal 052 to generate a quadraturesignal Q, the multiplier 430 multiplies the quadrature signal Q by thefactor Y to obtain an adjusted quadrature signal Qadj. Finally, theadder 418 adds the adjusted in-phase signal Iadj and the adjustedquadrature signal Qadj to generate a compensated in-phase signal Imatch.

The method for determining the delay parameter of the adjustable delayunit 414, the factor X of the multiplier 416 and the factor Y of themultiplier 430 are similar to the steps shown in FIG. 3, and only theformula for calculating the delay parameter of the adjustable delay unit414 is different from the formula for calculating the delay parameter Δof the adjustable delay unit 224 of the receiver 200 shown in FIG. 2 (inStep 306). Because a person skilled in this art should understand thefollowing calculations after reading the above-mentioned disclosure(e.g., the delay parameter of the adjustable delay unit 414 can becalculated by the formula:

${\Delta = {{- \frac{( {{Y\; 1} - {Y\; 2}} )}{\frac{2{\pi( {{f\; 2} - {f\; 1}} )}}{Fs}}} = {- \frac{( {{Y\; 1} - {Y\; 2}} )}{\frac{2{\pi( {{{tone\_ idx}( {f\; 2} )} - {{tone\_ idx}( {f\; 1} )}} )}}{FFT\_ pts}}}}},$that is a negative of the delay parameter described in the embodimentshown in FIG. 2), further descriptions are omitted here.

It is noted that, in the embodiment shown in FIG. 4, the first channel410 is the in-phase channel and the second channel 420 is the quadraturechannel. In other embodiments, however, the first channel 410 can be thequadrature channel and the second channel 420 can be the in-phasechannel, and the determination steps of the delay parameter Δ, thefactor X3 of the multiplier 416 and the factor Y3 of the multiplier 430are similar to the steps shown in FIG. 3 (only the formula forcalculating the delay parameter Δ is different from the formuladescribed in step 306). Because a person skilled in this art shouldunderstand how to derive the formula to obtain the delay parameter Δ andthe two factors X3 and Y3 after reading the above-mentioned disclosure,further descriptions are omitted here.

Please refer to FIG. 5, which is a diagram illustrating a gainmismatch/phase mismatch/path delay mismatch of an in-phase signal and aquadrature signal of a prior art transmitter 500, where the transmitter500 includes two mixers 510 and 520 and an adder 530; and a path delay540 shown in FIG. 5 is used to represent a delay difference between anin-phase channel and a quadrature channel, and is not a circuit element.As shown in FIG. 5, the transmitter 500 receives an in-phase signal Iand a quadrature signal Q, and the in-phase signal I and a quadraturesignal Q are processes by the mixers 510 and 520, the path delay 540 andthe adder 530 to generate an output signal Vout, and the output signalVout is radiated by an antenna. The local oscillation signals suppliedto the mixers 510 and 520 are (1+G)cos(w_(LO)t+P) and −sin(w_(LO)t),respectively, where “G” is a value of I/Q gain mismatch, “P” is a valueof I/Q phase mismatch, the “dt” is a value of I/Q path delay mismatch.Because the in-phase signal and the quadrature signal included in theoutput signal Vout may have the gain mismatch/phase mismatch/path delaymismatch, errors may be happened when the output signal Vout is receivedand processed by a receiver.

Please refer to FIG. 6, which is a diagram illustrating a transmitter600 according to one embodiment of the present invention. As shown inFIG. 6, the transmitter 600 includes a first channel 610, a secondchannel 620, a multiplier 630 and an adder 640, where the first channel610 includes a mixer 612 and a multiplier 614, and the second channel620 includes a mixer 622, an adjustable delay unit 624 and an adder 626.In addition, the transmitter 600 further includes a control unit (notshown) that is used to generate control signals according to the outputsignal Vout of the transmitter 600, and the control unit uses thecontrol signals to adjust a factor X of the multiplier 614, a factor Yof the multiplier 630 and a delay amount of the adjustable delay unit624.

In the operations of the transmitter 600, the multiplier 614 multipliesan in-phase signal I by the factor X to generate a first adjustedin-phase signal Iadj1, and the mixer 612 mixes the first adjustedin-phase signal Iadj1 with a local oscillation signal OS1 to generate amixed in-phase signal Imix. At the same time, the multiplier 630multiplies the in-phase signal I by the factor Y to generate a secondadjusted in-phase signal Iadj2, the adder 626 adds the second adjustedin-phase signal Iadj2 and a quadrature signal Q to generate an adjustedquadrature signal Dadj, the adjustable delay unit 624 delays theadjusted quadrature signal Dadj to generate a delayed quadrature signalQd, and the mixer 622 mixes the delayed quadrature signal Qd with alocal oscillation signal OS2 to generate a mixer oscillation signalQmix. Finally, the adder 640 adds the mixed in-phase signal Imix and themixer oscillation signal Qmix to generate the output signal Vout.

Please refer to FIG. 6 and FIG. 7 together, FIG. 7 is a flowchart of amethod for compensating a mismatch of the in-phase signal and thequadrature signal of the transmitter 600 according to one embodiment ofthe present invention. Referring to FIG. 7, the flow is described asfollows.

In Step 700, the adjustable delay unit 624 is disabled, that is thedelay amount of the adjustable delay unit 624 is set to be 0. Then, inStep 702, the transmitter 600 transmits a first test signal and a secondtest signal, where the first test signal and the second test signal arethe in-phase signal and quadrature signal, respectively, and each ofthem is a single tone signal having a frequency f1 (i.e., the first testsignal serves as the in-phase signal I shown in FIG. 6, and the secondtest signal serves as the quadrature signal Q shown in FIG. 6). Then,the control unit (not shown) adjusts the factor X of the multiplier 614and the factor Y of the multiplier 630 by referring to an imagerejection ratio (IRR) calculated by using the output signal Vout toobtain a first group of factors (X1, Y1), where when using the firstgroup of factors (X1, Y1) the transmitter 600 has the optimal IRR.Referring to FIG. 5 and FIG. 6, assuming that the oscillation signalssupplied to the mixers 612 and 622 are (1+G)cos(w_(LO)t+P) and−sin(w_(LO)t), respectively, the value of Y1 should be close to(−tan(P+2πf1*dt)) when the output signal Vout has the optimal IRR.

In Step 704, the transmitter 600 transmits a third test signal and afourth test signal, where the third test signal and the fourth testsignal are the in-phase signal and quadrature signal, respectively, andeach of them is a single tone signal having a frequency f2 (i.e., thethird test signal serves as the in-phase signal I shown in FIG. 6, andthe fourth test signal serves as the quadrature signal Q shown in FIG.6). Then, the control unit (not shown) adjusts the factor X of themultiplier 614 and the factor Y of the multiplier 630 by referring to animage rejection ratio (IRR) calculated by using the output signal Voutto obtain a second group of factors (X2, Y2), where when using thesecond group of factors (X2, Y2) the transmitter 600 has the optimalIRR. Referring to FIG. 5 and FIG. 6, assuming that the oscillationsignals supplied to the mixers 612 and 622 are (1+G)cos(w_(LO)t+P) and−sin(w_(LO)t), respectively, the value of Y2 should be close to(−tan(P+2πf2*dt)) when the output signal Vout has the optimal IRR.

In Step 706, the control unit uses the first group of factors (X1, Y1)and the second group of factors (X2, Y2) to calculate a delay amount ofthe adjustable delay unit 624. In detail, because in Steps 702 and 704it is calculated that: Y1≈(−tan(P+2πf1*dt)) and Y2≈(−tan(P+2πf2*dt)),the delay amount dt between the in-phase signal I and the quadraturesignal Q can be calculated by using the following formula:dt≈(Y1−Y2)/(2π(f2−f1)).

In addition, because dt=Δ*Ts=Δ/Fs, where Ts and Fs are a sampling clockperiod and a sampling clock frequency of an analog-to-digital converter(ADC) of the receiver 600, respectively, a delay parameter Δ used by theadjustable delay unit 624 can be calculated as follows:

${\Delta = {\frac{( {{Y\; 1} - {Y\; 2}} )}{\frac{2{\pi( {{f\; 2} - {f\; 1}} )}}{Fs}} = \frac{( {{Y\; 1} - {Y\; 2}} )}{\frac{2{\pi( {{{tone\_ idx}( {f\; 2} )} - {{tone\_ idx}( {f\; 1} )}} )}}{FFT\_ pts}}}},$where FFT_pts is a number of points used when performing a fast FourierTransform upon the first test signal and the second test signal, andtone_index is an index of the tone/frequency.

In Step 708, the control unit (not shown) enables the adjustable delayunit 624 and sets adjustable delay unit 624 according to the delayparameter Δ or the delay amount dt.

In Step 710, the transmitter 600 transmits a fifth test signal and asixth test signal, where the fifth test signal and the sixth test signalare the in-phase signal and quadrature signal, respectively, and each ofthem is a single tone signal having a frequency f3 (i.e., the fifth testsignal serves as the in-phase signal I shown in FIG. 6, and the sixthtest signal serves as the quadrature signal Q shown in FIG. 6). Then,the control unit (not shown) adjusts the factor X of the multiplier 614and the factor Y of the multiplier 630 by referring to the IRRcalculated by using the output signal Vout to obtain a third group offactors (X3, Y3), where when using the third group of factors (X3, Y3)the transmitter 600 has the optimal IRR. The third group of factors (X3,Y3) are used by the multipliers 614 and 630 of the transmitter 600 inthe following operations.

In light of above, after the delay parameter Δ used in adjustable delayunit 624, the factor X3 of the multiplier 614 and the factor Y3 of themultiplier 630 are determined, the transmitter 600 can eliminate thegain mismatch/phase mismatch/path delay mismatch of the in-phase signalI and the quadrature signal Q included in the output signal Vout. Whenthe output signal Vout is received and demodulated by a receiver, thegain/phase/path delay of the generated in-phase signal and quadraturesignal will be matched.

It is noted that, in the embodiment shown in FIG. 6, the first channel610 is the in-phase channel and the second channel 620 is the quadraturechannel. In other embodiments, however, the first channel 610 can be thequadrature channel and the second channel 620 can be the in-phasechannel, and the determination steps of the delay parameter Δ, thefactor X3 of the multiplier 614 and the factor Y3 of the multiplier 630are similar to the steps shown in FIG. 7 (only the formula forcalculating the delay parameter Δ is different from the formuladescribed in step 706). Because a person skilled in this art shouldunderstand how to derive the formula to obtain the delay parameter Δ andthe two factors X3 and Y3 after reading the above-mentioned disclosure,further descriptions are omitted here.

Please refer to FIG. 8, which is a diagram illustrating a transmitter800 according to another embodiment of the present invention. As shownin FIG. 8, the transmitter 800 includes a first channel 810, a secondchannel 820, a multiplier 830 and an adder 840, where the first channel810 includes a mixer 812, an adjustable delay unit 814 and a multiplier816, and the second channel 820 includes a mixer 822 and an adder 824.In addition, the transmitter 800 further includes a control unit (notshown) that is used to generate control signals according to the outputsignal Vout of the transmitter 800, and the control unit uses thecontrol signals to adjust a factor X of the multiplier 816, a factor Yof the multiplier 830 and a delay amount of the adjustable delay unit814.

In the operations of the transmitter 800, the multiplier 816 multipliesan in-phase signal I by the factor X to generate a first adjustedin-phase signal Iadj1, the adjustable delay unit 814 delays the firstadjusted in-phase signal Iadj1 to generate a delayed in-phase signal Id,and the mixer 812 mixes the delayed in-phase signal Id with a localoscillation signal OS1 to generate a mixed in-phase signal Imix. At thesame time, the multiplier 830 multiplies the in-phase signal I by thefactor Y to generate a second adjusted in-phase signal Iadj2, the adder824 adds the second adjusted in-phase signal Iadj2 and a quadraturesignal Q to generate an adjusted quadrature signal Qadj, and the mixer822 mixes the adjusted quadrature signal Qadj with a local oscillationsignal 052 to generate a mixed quadrature signal Qmix. Finally, theadder 840 adds the mixed in-phase signal Imix and the mixed quadraturesignal Qmix to generate an output signal Vout.

The method for determining the delay parameter of the adjustable delayunit 814, the factor X of the multiplier 816 and the factor Y of themultiplier 830 are similar to the steps shown in FIG. 7, and only theformula for calculating the delay parameter of the adjustable delay unit814 is different from the formula for calculating the delay parameter Δof the adjustable delay unit 624 of the transmitter 600 shown in FIG. 6(in Step 706). Because a person skilled in this art should understandthe following calculations after reading the above-mentioned disclosure(e.g., the delay parameter of the adjustable delay unit 814 can becalculated by the formula:

${\Delta = {{- \frac{( {{Y\; 1} - {Y\; 2}} )}{\frac{2{\pi( {{f\; 2} - {f\; 1}} )}}{Fs}}} = {- \frac{( {{Y\; 1} - {Y\; 2}} )}{\frac{2{\pi( {{{tone\_ idx}( {f\; 2} )} - {{tone\_ idx}( {f\; 1} )}} )}}{FFT\_ pts}}}}},$that is a negative of the delay parameter described in the embodimentshown in FIG. 6), further descriptions are omitted here.

It is noted that, in the embodiment shown in FIG. 8, the first channel810 is the in-phase channel and the second channel 820 is the quadraturechannel. In other embodiments, however, the first channel 810 can be thequadrature channel and the second channel 820 can be the in-phasechannel, and the determination steps of the delay parameter Δ, thefactor X3 of the multiplier 816 and the factor Y3 of the multiplier 830are similar to the steps shown in FIG. 7 (only the formula forcalculating the delay parameter Δ is different from the formuladescribed in step 706). Because a person skilled in this art shouldunderstand how to derive the formula to obtain the delay parameter Δ andthe two factors X3 and Y3 after reading the above-mentioned disclosure,further descriptions are omitted here.

Briefly summarized, in the method for compensating gain mismatch/phasemismatch/path delay mismatch of an in-phase signal and a quadraturesignal of a receiver or a transmitter of the present invention,parameters for compensating the gain mismatch/phase mismatch/path delaymismatch can be determined correctly and efficiently, and prevent errorsin the following operations.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

What is claimed is:
 1. A method for compensating a mismatch of anin-phase (I) signal and a quadrature (Q) signal of a receiver, whereinthe receiver comprises: a first channel, comprising: a first mixer, formixing a received signal with a first local oscillation signal togenerate a first signal; a first multiplier, coupled to the first mixer,for generating an adjusted first signal according to the first signal;and an adder, coupled to the first multiplier; a second channel,comprising: a second mixer, for mixing the received signal with a secondlocal oscillation signal to generate a second signal; and an adjustabledelay unit, coupled to the second mixer, for delaying the second signalto generate a delayed second signal; and a second multiplier, coupledbetween the adjustable delay unit and the adder, for generating anadjusted second signal according to the delayed second signal, whereinthe adder adds the adjusted first signal and the adjusted second signalto generate a compensated first signal; wherein the compensated firstsignal is one of the I signal and the Q signal, and the delayed secondsignal is the other one of the I signal and the Q signal; and the methodfurther comprising: disabling the adjustable delay unit; receiving afirst test signal to serve as the received signal to determine a firstgroup of factors of the first multiplier and the second multiplieraccording to an image rejection ratio (IRR); receiving a second testsignal to serve as the received signal to determine a second group offactors of the first multiplier and the second multiplier according toanother IRR; and calculating a delay amount of the adjustable delay unitaccording to the first group of factors and the second group of factors.2. The method of claim 1, wherein each of the first test signal and thesecond test signal is a single tone signal, and frequencies of the firsttest signal and the second test signal are different.
 3. The method ofclaim 1, wherein each of the image rejection ratios are calculated byusing the compensated first signal and the delayed second signal.
 4. Themethod of claim 1, further comprising: after calculating the delayamount of the adjustable delay unit, enabling the adjustable delay unit,and setting the adjustable delay unit by using the delay amount; andreceiving a third test signal to serve as the received signal todetermine a third group of factors of the first multiplier and thesecond multiplier.
 5. The method of claim 4, wherein the step ofdetermining the third group of factors comprises: receiving the thirdtest signal, and determining the third group of factors of the firstmultiplier and the second multiplier according to an image rejectionratio.
 6. A method for compensating a mismatch of an in-phase (I) signaland a quadrature (Q) signal of a receiver, wherein the receivercomprises: a first channel, comprising: a first mixer, for mixing areceived signal with a first local oscillation signal to generate afirst signal; an adjustable delay unit, coupled to the first mixer, fordelaying the first signal to generate a delayed first signal; a firstmultiplier, coupled to the adjustable delay unit, for generating anadjusted first signal according to the delayed first signal; and anadder, coupled to the first multiplier; a second channel, comprising: asecond mixer, for mixing the received signal with a second localoscillation signal to generate a second signal; and a second multiplier,coupled between the second mixer and the adder, for generating anadjusted second signal according to the second signal, wherein the adderadds the adjusted first signal and the adjusted second signal togenerate a compensated first signal; wherein the compensated firstsignal is one of the I signal and the Q signal, and the second signal isthe other one of the I signal and the Q signal; and the method furthercomprising: disabling the adjustable delay unit; receiving a first testsignal to serve as the received signal to determine a first group offactors of the first multiplier and the second multiplier according toan image rejection ratio (IRR); receiving a second test signal to serveas the received signal to determine a second group of factors of thefirst multiplier and the second multiplier according to another IRR; andcalculating a delay amount of the adjustable delay unit according to thefirst group of factors and the second group of factors.
 7. The method ofclaim 6, wherein each of the first test signal and the second testsignal is a single tone signal, and frequencies of the first test signaland the second test signal are different.
 8. The method of claim 6,wherein each of the image rejection ratios are calculated by using thecompensated first signal and the second signal.
 9. The method of claim6, further comprising: after calculating the delay amount of theadjustable delay unit, enabling the adjustable delay unit, and settingthe adjustable delay unit by using the delay amount; and receiving athird test signal to serve as the received signal to determine a thirdgroup of factors of the first multiplier and the second multiplier. 10.The method of claim 9, wherein the step of determining the third groupof factors comprises: receiving the third test signal, and determiningthe third group of factors of the first multiplier and the secondmultiplier according to an image rejection ratio.